Electric furnace



Jul 21, 1925.

A. RUCKSTAHL LECTRTC FURNACE Filed May 11, 2 Sheets-Sheet 1 dummy;

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July 21, 1925.

v Y A. RUCKSTAHL ELECTRIC FURNACE Filed May 11, 1922 2 Sheets-Sheet 2liililliilIii: :fjllllffj Patented July 21, 1925.

UNITED STATES ALFRED RUCKSTAHL, OF DETROIT, MICHIGAN.

ELECTRIC FURNACE.

Application filed May 11, 1922. Serial No. 560,188.

T 0 all whom it may concern:

Be it known that I, ALFRED RUoKs'rAHL, a citizen of the United States ofAmerica, residing at Detroit, in the county of Wayne and State ofMichigan, have invented certain new and useful Improvements in ElectricFurnaces, of which the following is .a specification, reference beinghad therein to the accompanying drawings.

This invention relates to electric furnaces suitable for the treatmentof material at high temperatures.

The objectof the invention is to provide a furnace of the circular typewithin which material may be made to travel past a series of heatingelements adapted for easy removal and replacement.

A further object of the invention is the provision with a furnace of thetype described of a series of interchangeable elec trical heatingelements of different heating characteristics whereby the temperatureconditions within the furnace may be varied by the substitution of oneelement for another.

A still further object of the invention is the provision of anelectrically heated furnace havin a rotating carriage forming the lowerwal of the annular chamber and having a continuous series of electricalresistance elements extending across the upper portion of the chamberwhereby work placed upon the rotary carriage will be exposed to heatfrom above.

Another object of the invention is the provision of an electricresistance unit which may be cheaply and economically construoted, whichwill maintain its rigidlty substantially unimpaired at high temperatureand which is adapted for ready insertion into and removal from itsposition within a furnace. I

In the drawings,

Figure 1 is a horizontal section partially diagrammatic through aportion of a furnace constituting one embodiment of the invention;

Fig. 2 is a vertical central section;

Fig. 3 is a fragmentary perspective View of a portion of the furnace,parts being broken away;

Fig. 4 is a plan view of a preferred form of resistor element;

Fig. 5 is a side elevation thereof, a portion being shown in section onthe line V-V of Fig. 4, and

Fig. 6 is a perspective View of a modified form of resistor element.

In the embodiment of the invention shown in the drawings, the furnace ismade in the form of a ring or annulus 1, mounted upon suitable supports2 carrying horizontal beams 3 from which depend supports 4 secured tothe inner wall of the annulus.

The outer wall of the furnace is preferably provided with the'nsualmetallic jacket 5 within which is an insulating layer 6 of any suitablematerial such as sil-o-cel surrounding an annular chamber 7 providedwith a lining 8 of a refractory material.

A central supportin shaft 9 rests at its lower end within a soc et 10and is held at its upper end within a member 11 carried by the beams 3.The central portion of the shaft 9 is screwthreaded at 12 to receive anadjusting nut 13 upon which is mounted a ball bearing 14 for a. collar15. Carried by the collar 15 are adjustable sus ension rods 16, theouter lower ends of w 'ch are secured at 17 to beams 18. .Upon theouterends of the beams 18 which extend radially from the central shaft 9 isan annular carriage 19. The carriage 19 is provided with a layer ofinsulating material 20 upon which is supported a bed 21 ofa suitablerefractory material. As shown in Fig. 2, the bed is stepped, the innerportion 22 being some what higher than the outer portion 23 for apurpose later to be described. The carriage 19 has inner andouterchanneled portions 24 and 25 containing sand which cooperates withdownwardly extending flanges upon the metal members 26 and 27 to form asealto prevent the loss of heat from the interior of the chamber 7.

The annular carriage 19 is preferably supported entirel from the shaft 9and by the adjustment 0 the rods 16 and the collar 15 the carriage maybe raised or lowered to provide proper clearance as it rotates withinthe chamber 7. Extending around the sides of the annular chamber 7 areopenings adjacent to the roof ofthe chamber and preferably extendingthrough the outer peripheral wall of the furnace as-illustrated in Figs.2 and 3, though it will be obvious that the openin s might be formedwithin the interior we of the annular chamber if desired, as indicatedat 29. These openings will form a substantially continuous seriesextending throughout the entire circumference of the furnace and eachopening will be of a size permitting the insertion therethrough of anelectric resistance element 30. The openings 28 may be closed by meansof bricks 31 adapted to fit closely within the openings and some of thebricks may be provided with apertures 32 through whlch the terminals 33of the resistor elements 30 may extend to the outside of the furnace. Asan additional insulating means, plates 34 of asbestos or! similarmaterial may be secured as by bolts 35 over the outer ends of thebricked-in openings 28. The furnace will be provided with inlet andoutlet doors 36 and 37 which may have any suitable form of closure (notshown) The resistor elements 30 will preferably be made of an alloyhighly resistantto heat and oxidation. Such an alloy may consist ofnickel and chromium, or of nickel, chromium and iron with or without thepresence of other elements such as manganese and silicon. The specificalloy forms no part of the present invention and may be varied to suitconditions.

The preferred structure for :the heating elements will be thatillustrated in Figs. 4 and 5 in which the element consists of-aplurality of channeled portions each arched as shown in Fig. 5, saidchanneled portions lying substantially parallel with each other as shownin Fig. 4 and connected at their adjacent ends alternately by solidsections 38 having a rib 39 formed thereon closely adjacent to the innerside of the connection. Resistor units of this form may conveniently beformed by casting, the arch shape and channeled cross section affordinggreat rigidity to prevent sagging of the elements when heated to veryhigh temperature; The ribs 39 are providedat the adjacent ends of thestraight portions to provide an increased cross section to preventexcessive heating of the element at that point as would occur if thematerial were left of uniform thickness.

In small furnaces,whe're the span is not excessive, a simpler form ofresistance element may be used, this modification'being illustrated inFig. 6. This form of element may consist of a ribbon 40 having aseriesyof bends 41 connecting a series of parallel or slightly divergentportions 42, the bends being substantially in line with each other ateach end. In either case, the resistor element may readily be passedthrough the openings 28 into position within the upper portion of thefurnace just beneath the roof, the inner ends of the element resting inrecesses, 43 formed in the side walls of the refractory lining -8.

uously or intermittently by means not illustrated and assuming that therotation is counterclockwise in Fig. 1, articles to be treated may beintroduced through the doorway 36 onto the bed 21. The step 22 remotefrom the doorway 36 is higher, than the step 23 so that articles restingupon the inner step. 22 may be placed in position or removed therefromwithout interfering with articles upon the step 23. As the carriage 19rotates, the articles introduced through the door? way 36 will bebrought within the range of radiation of the elements 30 and if anincrease in temperature during the pro ress of the material is desired,suitable e ements will be located at proper intervals about the annularchamber to produce the desiredprogressive alteration in temperature. Itwill be evident that this variation in temperature may readily beproduced by the proper selection from among the interchangeable units ofthose possessing the desired heating characteristics and theintroduction of such elements through the side openings 28 at properplaces around the circumference of the circle. Thus for example,material introduced at the doorway 36 may first be raised rapidly to acertain temperature, maintained at that temperature, for a predeterminedportion of its path and then lowered in temperature during the.remainder of its progress by the proper selection of heating elementsfor introduction into the series within'the range of which the materialis brought as it travels through the annular chamben, On'the other handat the will of the operator, certain elements may be withdrawn andothers. substituted so that within a short time thev furnace may beadapted" for an entirely different range of heating in whichmaterialintrodu'ced at' the doorway 36 will be slowly raised intemperature, reaching its maxlmum only as it reaches the doorway 37.This flexibility of operation is obvious- 1 ly impossible in theordinary type of electric furnace at present in use in which the heatingelement consists of a continuous ribbon suspended from insulator membersupon the side walls of the furnace. A further advantage of the presentconstruction is the readiness with which any break occurring within theheating system may be located by the application of atesting instrumentto, the exposed terminals. Whenever a break occurs, the broken elementmay be removed with a minimum loss of time and another elementsubstituted therefor with out waiting for the furnace to cool andwithout the necessity of removing the material being treated from thefurnace.

Certain' features of the present invention are also disclosed inapplication, Serial No. 560,186 filed con.-

The. carriage 19 may be rotated continsacurrently herewith.

my co-pending It will be obvious that many changes and modifications maybe made in the details of construction without departing from theprinciple of this invention or sacrificing any of its advantages. Theinvention is therefore claimed in any of its forms or modificationswithin the legitimate and valid scope of the appended claims.

I claim:

1. An electric furnace comprising a wall having a lining of refractorymaterial enclosing an annular chamber, a bed forming the bottom of saidchamber, a central supporting shaft, suspension members carried by saidshaft, and means carried by said suspension members, said beams forminga support for said bed, the furnace being of general annulararrangement, the suspension members being located to be supported by theshaft above the plane of the beams and within the central zone of thefurnace.

2. A structure as in claim 1, in which the suspension members areadjustable to raise and lower said supporting means.

3. A structure as in claim 1, in which the suspension members, the beamsand the bed carried thereby are mounted for rotation about said centralsupporting shaft.

4. An electric furnace comprising an enclosure provided with an annularchamber therein open at the bottom, an annular bed mounted withinthebottom of said chamber, and a support for said bed adapted to permit therotation of said bed within said chamber, said support being providedwith adjusting means whereby to control the independent verticaladjustment of various portions of said bed, the furnace being of generalannular arrangement, the suspension members being located to besupported by the shaft above the plane of the beams and within thecentral zone of the furnace.

5. An electric furnace comprising an enclosing furnace wall having alining of refractory material therein surrounding the top and sides ofan annular chamber formed within the furnace, said furnace wall having aplurality of openings throughout its periphery of a size adapted topermit the passage of electric heating units, and a plurality ofremovable electric heating units arranged substantially radially of saidchamber and forming portion of a non-arcing circuit.

6. An electric furnace having an annular chamber therein, said chamberhaving a bed forming the floor thereof and adapted for movement withinsaid chamber whereby material placed upon said bed will be carried in'asubstantially circular path through said chamber, and a plurality ofinterchangeable electric heating units arranged substantially'radiallyof said chamber and forming a portion of a non-arcing circuit, saidunits being adapted for insertion at chamber and a plurality ofinterchangeable removable electric resistance units arrangedsubstantially radially of said chamber in a series extendingsubstantially throughout I the entire circumference of said furnace,said units forming a portion of a non-arcing circuit.

8. An electric furnace having an annular chamber therein and a bedforming the floor of said chamber and mounted for rotary movement, saidbed being provided with inner and outer steps, the surface of the bedtoward the inner portion of the chamber being higher than the surface ofthe outer portion, the chamber having a passageway, the lower portion ofwhich is opposite the lower outer step of the rotary bed, wherebymaterial introduced into said chamber through said passageway may beplaced upon said upper inner step without interfering with material uponsaid lower outer step.

9. In a furnace for heat-treatment of metallic objects, a chamber havinga refractory lining within which the objects are movable in an advancingdirection, and

means for producing the treatment temperatures within such chamber, saidmeans including' an electric circuit of the nonarcing type, saidcircuit. including a succession of individual heating units within thechamber and collectively connected to complete the circuit andindividually removable to permit substitution of units.

10. In a furnace for heat-treatment of metallic objects, an annularchamber having a refractory lining and within which the objects aremovable in the direction of length ofthe chamber, means for producingthe treatment temperatures within such chamber, said means including anelectric circuit of the non-arcing type, said circuit including asuccession of individual heating units operably connected to completethe circuit and individually removable in radial directions of thefurnace assembly to permit substitution of units.

11. A furnace as in claim 10 characterized in that the units arearranged in series relation within the circuit.

12. A furnace as in claim 10 characterized in that the heating units arearranged at the top of the chamber above the objects being treated.

13. A furnace as in claim 10 characterized in that the heating units arearranged adj a.- cent but s aced from the top of the chamber.

141. A urnace as in claim 10 characterized in that each unit is of thegrid-type with an overall dimension in the direction of width of thechamber at least equal to the width of such chamber.

15. A furnace as in claim 10 characterized in that a vertical Wall ofthe chamber is provided with an opening through which an individual unitmay be inserted and removed.

16. A furnace as in claim 10 characterized in that a vertical wall ofthe chamber is provided with an opening for and individual to each unitto permit individual insertion and removal of a unit at will.

17. In an electric furnace, wherein the furnace walls having a lining ofrefractory material, and wherein the furnace is adapted to permit themovement therethrough of articles or material to be treated by thefurnace, said furnace having one of its walls formed with a passagewayof a size to permit insertion and removal bodily of a resistor unit,said furnace having a support for the resistor unit when the latter isin 'position for active service, and a resistor unit having a form anddimensions to be supported Within the furnace and be movable throughsuch passageway, the movement of the resistor unit to and from serviceposition being in directions substantially transverse to the directionof travel of the material or articles through the treatment chamber ofthe furnace.

18. In an electric furnace, a chamber having a refractory lining andwithin which the objects or material to be treated are advanced througha generally predetermined travel path, and means for producing thetreatment temperatures within the chamber, said means including anelectric circuit of the non-arcing type, said circuit including asuccession of individual heating units combinedly connected to completethe circuit and individually removable to permit substitution of units.

19. A furnace as in claim 18 characterized in that the direction ofmovement of a unit to and from service position is substantiallytransverse to the direction of advance of the articles or material to betreated within the chamber.

20. A furnace as in claim 18 characterized in that a wall of the furnaceis formed with individual passageways through which the units aremovable to and from'service position.

21. A furnace as in claim 18 characterized ALFRED BUCKSTAHL.

,lVitnesses CHAS. W. STAUrrIenR;

ARTHUR MINNICK.

